Filters or other devices implemented in integrated circuits may use components known as resonators to generate resonant frequencies. Resonators, however, may experience the problem of spurious responses. A spurious response is any unwanted signal on a frequency other than the resonant frequency (e.g., the frequency being broadcast or received). Devices experiencing spurious frequency responses operate in spurious mode. A resonator that operates in the spurious mode creates noise and other problems in the overall circuit design of the filter, or any other device that incorporates the resonator.
The mismatch between the coefficients of thermal expansion of multiple materials making up a resonator may lead to excessive thermal stress. Undue amounts of thermal stress leads to stress imbalance, which may result in problems such as beam buckling, damage to the resonator structure, or other spurious mode irregularities.
Resonators may be acoustically coupled such that the electrical signals transmitted through the resonator are transferred electromechanically. Resonators may also extend in a lateral fashion, or be horizontally constructed. Often, such horizontal resonators have components, such as electrodes, that are symmetrically structured. Resonators may also be symmetrical and arranged in a horizontal structure, or implemented in microelectromechanical systems (MEMS). Nevertheless, such MEMS resonators may experience problems such as spurious responses, operation in the spurious mode, or thermal stress, as discussed above.